Two-way polar telegraph system



v Feb. 7, 1950 s. A. BAFQRETT 2,496,372

TWO-WAY POLAR TELEGRAPH SYSTEM Filed June 3, 1944 ATTORNE 5 Patented Feb. 7, i950 UNITED STATES PATENT OFFICE TWO-WAY. POLAR TELEGRAPH SYSTEM Sidney Alfred Barrett, Montreal, Quebec, Canada Application June 3, 1944, Serial No. 538,572 In Canada June 12, 1943 'Claims. It

The invention relates to improvements ina self! compensating, telegraph system for'transmitting signalling impulses over communication lines,.and more particularly, for transmittingthese impulses over long open-wire lines subjected to varying weather and leakage resistance conditions and alsoto extreme changes iniseries line resistance, such as that occasioned by changing from lines of widely different values of series resistance.

The invention consists essentially of :the novel features of a telegraph system as pointed out in the claims for novelty followingja description con-v taining an ex lanation in detail of acceptable forms of the invention.

In previous systems ivarying leakage resistance of the line, and relatively largechangesin the series resistance of the line; made it'necessary to adjust the receiving equipment" 'connected'to the line at rather frequent intervals'to' compensate for these changes in the resistance characteristics of the line; so that the'received signals'wouldbe received without bias.

These adjustments are'verynndesirable; and add to thecost of the'equipment, especially so at a telegraph subscriber's station remotely "re-- moved from the central'telegraph'station or repeater point.

It is an object ofthis invention to arrange an impulse transmitting system in" which no' variable apparatus is'required in the transmitting or receiving'equipment, this equipment being arranged in such a manner that automatic compensation takes placeduring varying weather conditions and/or large changes in series resist ance of the line.

It is a further objectof this invention to provide a telegraph'system in-which the-apparatus at each end of the line applies similar signalling conditions to the line to transmit similar condi-' tions or impulses.

Still another object of this invention is'to provide telegraph line circuitbetween two telegraph stations either or both of which may b'ea central station or an outlying station, the operation of which is automatically self-compensating for chan es in the insulation resistance of theline and/or changes in the series 'of'the line:

In accordance with a specific embodiment of this invention two-telegraph stations areconnected together by a telegraph lineor channel, apportionof which includes open wire line subjected to varyingweatherconditicns and thus to varying leakage resistance; andalso to changes in seriesresis'tance-due to anychanges caused.

by'changing the'line from wires of onegauge-to that'of another gauge; Similar line and-receiving relays are connected :to this-line at each of the stations for responding to the-signalling condi tions transmitted. from the opposite end of the Means arez-provirled'at each'statiomwhereb'y-the line relays reverse the polarity applied at the receiving end of the line in response to reversals of polarities applied .to the sending end of the line. Thus the receiving relays respond to the signal conditions transmitted to them by the line relay without bias due to variations in the leakage resistance of the line, and/or changes in the series resistance of 'the line, these changes being automatically compensated for during the transmission of the signallingimpulses.

The term bias as used in this specification and applied to signal impulses, indicates a lengthening or shortening of the signal conditions or impulses. Marking bias, for example, means that the marking impulses are lengthened while the spacing impulses are shortened, whereas spacing bias means that the spacing'impulses are lengthened while the marking impulses are shortened. Signal impulses containing bias are' much less satisfactory for operating telegraph apparatus than those in which no bias exists, While signals having no bias are much more satisfactory for operating telegraph apparatus.

A common cause of this lengthening and shortening of the various signallin' conditions or im'- pulses is the marking current being greater than the spacing current, thus causing marking bias, and conversely, if the spacing current is greater than the marking current, spacing bias will exist. In other words, the marking and spacing currents are of unequal value. The unequal currents cause the receiving device to respond differently to the two signalling conditions, thus adding a bias to the received si nals.

However, in accordance with this invention the two signalling conditions always differ the same amount since the changing line conditions are compensated for automatically'from an established flux condition of the line relays, these unbiased signals being repeated into the windings of the receiving relays. The term marking is used to designate the line or signalling condition dur= ing the time when no impulses are being transmitted but the system is energized and ready to transmit signalling impulses. The term spac-- ing designates the other'signal or line-condition. The invention will be described in connection with the accompanying drawing in which Figure 1 shows a preferred arrangement of the inven tion as embodied at two central oflice telegraph stations, A and B.

These stations are connected together by line [0 which is composed of "resistance H and resistance l2.- Line 10 is'als'o subject to a leakage resistance which is represented by a concentrated resistance l3 which is shown connected to line In at point I 4. Point l4 need not be the electrical centre of the line but in order to simplify the explanation it will beassumed that this point is at the centreof the line.

.Atfistations .A and B- line-lll connects to'the upper winding of line relays l5 and It. The lower winding of these two relays are provided with a fixed amount of marking current from negative potentials H and I8. Thus line relays I5 and I6 are held to their marking contacts.

Receiving relays l9 and 20 are held to markings by negative polarities connected to the marking contacts of send relays 2| and 22 respectively. Send relays 2| and 22 are held to their marking contacts by marking current in their upper or operating windings which is approximatelytwice the value of their lower or bias windings. Control relays 23 and 24 are held to their marking contacts by marking current in their upper or operating windings, which is approximately one third greater than the spacing current in their lower or bias windings. When the system is in the marking or non-signalling condition, no current flows in the lower or looking windings of the control relays 23 and 24.

Assume first that station A is transmitting signal impulses to station B. Sending relay 2| and control relay 23 will be moved to their spacing contact in response to signals originating in the sending contacts 43. Marking current will flow in the line windingsof lin relay l5 and spacing current will flow in the line winding of line relay H5 at B. If the line current in the line winding of line relay it at B is slightly greater than the marking current in its lower winding the armature of this relay will move from its marking contact. Spacing current flowing over the line I0 will flow through both windings of relay It to ground3| and its armature will move to its spacing contact. Simultaneously a portion of the current flowing over line H! will flow through the windings of receiving relay 20 to ground 26 to move-its armature to its spacing contact.

When the line relay 6 at B reaches its spacing contact its armature will be connected to positive potential 21 via the armature and marking contact of control relay 24. Like potentials will now be connected to each end of the line and if there is no leakage on line H], no current will flow in the upper or line windings of line relay If) at A and I6 at 13.

Since line relay l6 at B is now connected to positive potential 21, the current in its lower winding will have a spacing effect upon its armature, and since positive potential 21 is of the same value as negative potential l8 at B the same amount of current will flow in its lower windings, and since positive potential 28 at A is of the same value as positive potential 21 at B there will be no current flowing in line H) unless there is leakage on the line.

From this it can be seen that provided there is sufficient current flowing in th line when send relay 2| is on spacing to move line relay l6 armature away from its marking contact, the series resistance of the line is of secondary importance, since with either minimum or maxirent will flow in the lower or bias winding of send relay 22 and th middle or bias winding of control relay. 24 to ground 32. Consequently these two-{relays'will have their 'arma'tures held on their marking contacts when a spacing signal is received by receiving relay 20.

mum line resistance, relay H5 at station B will have its armature moved with the sam force .to space as to mark.

It will be noted here that when receiving relay 20 at station B is moved to its spacing contact positive potential 33 will oppose positive potential 34 and no current will flow in the upper windings of send relay 22 and control relay 24. Likewise, no current will'flow in printer magnet 29 and the receiving device or printer magnet will register a spacing signaL- Due to the duplex :bridge arrangementghowever, marking cur- Control relays 23 and 24 at station A and B respectively, are provided to maintain a negative or marking potential on the marking contact of the send relay during transmission. For example, when a spacing impulse is transmitted from station A to station B, control relay 23 moves to itsspacing position and connects negative or marking polarity I! to the windings of receiving relay is via thespacing contact of line relay [5, thus holding're'ceiving relay I9 on its marking contact, while at the same tim retaining a marking or negative potential on the marking contact of send relay 2| while its armature is resting on its spacing contact. It is obvious from this, that when send relay 2| is restored to its marking position, negative or marking polarity I! will be connected to the line at station A in opposition to positive or spacing potential 2'! at station B. It will be noted here that during the time send relay 2| at station A is moving from its spacing to its marking contact, spacing current is flowing from positive potential 2! at B, through both upper and lower windings of line relay |5 at station A in a direction eifective to hold its armature On its spacing contact, thereby retaining marking potential I! on the marking contact of send relay 2| and a marking current in windings of receiving relay I9.

When send relay 2| at station A reaches its marking contact, current flows over line H] from positive potential. 2'|.at station B to negative potential IT. The current in theline winding of line relay It at station B is marking, while th line current, in the line winding of line relay l5 at station A is spacing. This condition will prevail until line relay l6 at station B has its armaturemoved away from its spacing contact by the marking current flowing in its upper or line winding. After line relay at station B has its armature moved away from its spacing contact, current will flow over line ID from negative potential I! at station A through both windings of line relay l6 to ground 3|, this current being in a direction to move its armature to its marking contact. Simultaneously, marking current will flow through the windings of receiving relay 2!] at station B, and its armature will be moved to marking.

It should be noted here that-during the time send relay at station A is moved from space to mark, that control relay 23 is locked to spacing by spacing current in its lower or locking winding via the spacing contact of line relay l5 adding to the spacing current in its middle or bias winding. The combined effects of these two spacing currents is sufiicient, due to the shunt around its upper or operating winding, to overcome the effect of the marking current in its upper winding, until line relay l5 leaves its spacing contact and releases the spacing current in the lower winding of control relay 23, hence line relay |5 now unlocks relay 23.- In other words, control relay remains locked to spacing until the line i5 control -r,e1ar; to spacing as described, until. the

managers 5 Saline rr'elay at I thez'receiving een'd :has rresponded ttotthermarkingpulse.being:transrnitted. .Bythis 311188.115, the'receivingrrelayi I 9 at-istationA,i.or're ceiving relay 20 at station B, is held to Lmarking duringatransmission" fIOIIliStBJIiOIL'ATOf B respec- :tively.

;It isapparent from theabove that line'relay- I6 cat'istation'..B is made to respond'toimarkingand :ispacing impulses 2 transmitted fromsstation :by ssen'drelayiZ I :in such-ta: manner that the. potenttoreverse, .that is. to say,- a positive-polarity: for-a C's-pace pulse,-'and a negative 'polarity 'for amark gpulse. These reversals of polarity opposingthose cconnected atthe'sending end of'the line, simuletaneously reversing the current in the lower windings 'of either linerelay I5 at station "A-zor line relay iii-at station B, depending upon'the direction of: transmission. It is to be understood ithatithesoperation and function'ofthe line, re-

rceive,:cntrol and-:send'relays at-station B func- Ction .in the manner described for transmission from station A in a like manner.

.lIt:=should -be' further apparent that since' the :tmarkingan'd spacing currents in the'windings of l line-:relay rfiand receiving relay 20 =atstation B are of 'the same value and their al'gebraicsum aequal to zero,- there willbe no bias due to changes .in the series'resistance of the line.

.It can be'further'shown that the above is true -for' lines having leakage from the following:

Assume, for example, that line I0 -is subjectto leakage .as shown by resistance I3. When the ::system is in the marking or non-signalling con- -:dition current willfiow over line Iflcomprising :resistancesII and I2. This current-.will-have-a :spacingr; effect upon the armatures of line relays r I5. and I6 at station A and B respectively. Proividing itis not suflicient to overcome the mark- ;ing: current'in the-lower windings of these re- .lays, their armatures will remain on marking. If :now, for exampleya spacing impulse is transmitted from station A to --B, as descri-bedabove, :positive potential 28 and positive potential 21 at :station A andB respectively, will be connected .-to the line. Current frompositive potential '21 will flow through the line windings of relay I6 "at station B over some portion of the line to ground through the leakage path. 'This current 'will have a marking effect upon the armature of relay I6. The only effect of this current willbeto .reduce the effective spacing current in its lower :winding and, since the applied voltage at points and 42 are at the same potential for both con- "clitions of-signalling, the marking'current in'the line winding of line relay I6 will be of the same *value as the space current due to leakage when -'-the system is in the marking condition. In other words, the algebraic sum of these "two leakage currents-is equal-to zero, and the signal transmitted by send relay2l will be-received by line relay I6 at station B without bias. Likewise, the .resultant magnetic efiectsofzthetmarking and spacing currents in the lower windings'of line re-- lay I6 willhave theiralgebraic sum-equal to zero. Therefore, there can be no bias in the received signal'due to a leakage.

"It will'be noted however, that during. periodsrof flow insulation the'amount o'f.marking.and.spac- 4 :ing current during" the travel-time of .thegarmature of relay I6 will be reduced, .as compared-to the no leakage condition. However, since these two currents are equally attenuated, there will be no bias on line relay I6 from this source. It will the furtheri notedt'thatithe anarldng andsspacing currents in the windings of receiving :reiay i2 0 will. also -be:attemiated equallytduringithis period,

hence no biasnistortion will appear intthew-ind- 'ings ofithisrelay inithe signals transmitted from sending relay 2| at station A.

It is apparent from the above (lescription,.that

the impedance of -the line is the :same for both vcond'itionsmf signalling; that: is: to 'say,the:-Lsame amount- 0f "current will 1 flow overttheline for-3a tia'ls. connected to'the line :atstationl-B are made anarking impulse as for a spacing 1 impulse from "either send relay I or 22. It follows I therefore, 'that-the armaturesof line relays l5t'an'd I6,-1idepen'ding :upon the direction of I transmission, will :1 have their armatures moved from either their marking'or spacing'contacts by the same amount -ofcurrent, -irrespective of thevalue: of the series resistance-of r the line, providing this resistance "does not exceed the' maximum 1 value. In other words, P the "algebraic :sumof'these two currents will: 'bezero-regardless of line: resistance. There- :fore there-ai ill be 'no 'biasin the signals received from eitherstation .A or .station :3 i from i this source.

It followsifrom the :abova thatunder *all coni ditions J of signa'll'ingfnobias can be introduced into the :received signals, either from large changes infithe series resistance of the lineitself, or from: largeflchangesin I the leaka'ge .resistance of the line. wonsequently, it is not necessary to provide adjustable biasing means in eitherthe send'ingfi rorrreceiving apparatus: at "either end or r the: line to compensate forv the above'changesin thatcharacteristics ofzthe line.

3POSitilZei'pOt6I 1tia1S545 Pand :34Jarerof like vahie :but set opposite :polarity Ito those connected to rpotentialsilifl .8l'd i38 'WhiChIzaI'ElCDIHIfiCIidWOLthe markingmontactsoftreceiving relays I 9 an'd'2llre- :spectivelwconsequently: rovidingirapproximately ttwice'the amount ofsmarking current'inthe upper lwinding ;t-han :of ztspacing Jcurrent .in t-the' lower windings :of zsend: relays i2 I :an'd222 atrstation A -andiB"respectively. LDzieTtoxthe-sshunt around'ithe topper-windings i-of :controlfrelays 23*an'd 2 4 howisceventthermarkmg"current in theiupper windings of these relays effectively -reduced "to approxiz mately' only T0118" third greater than the spacing :current in their middle or bias windings. The purpose ofrtheilower. :or' looking windings of control'rrelays"23 .and 24 1 :is as 1 previouslydescribed, ttozhold'itsz'rarmature" to spacingthusholdingthe receiving relays I9 and 20 on their'marking con- -tacts"during.: theitransmission. from either station or :B'rrespectively. When (either receiving irelays I9 and '20 at r-stationsrAioriBrrespectivelyare on their spacing ccontactsz-there' will be no "current in the upper z'wlrrdings ofccontrol andisenct relaysl23,124, 2| and d2z-at stations ArorzBr respectively, since the posi- .-tive potential son the spacing montacts of 'receiving rre'lays I 9 -or E20 i opposes the 1 positive po- -tentia'1s-'s45:andi34- depending upon'the direction cofl transmission. iHowever; whenteitherreceivin'g rrelay Ifilordllareorr-their spacingcontacts, markzing ccnrrent rflonw in the zlower windings :of .1 'sendtrelays 2 lsandflztrespectively -and'through'the :uniddle iwiridings :of szcontrol relays "23 and 124 irespectively. Both of :thesetrelays therefore-will :be :held tottheir marking 'rcontacts "when either zreceivlngzrelay [F9 cor 220 "are 1'. on' their respective spacing :pontacts, depending upon :the direction to'f transmission. .aItaisitmbe' understoodi-that t-the windings of relays 2| and 23, and 22 and 24, have their windings connected differentially. In other words, relays 2| and Hand 22 and 24 respond only to signals originating in sending contacts 43 and 44 respectively.

' The invention is not to be construed as limited to the specific form that has been disclosed herein for illustration, but its scope is defined in the claims.

What I claim is:

1. A telegraph communication system comprising a line, first and second stations connected to each end of said line, sending contacts located in each of said stations, polarized relays at each end of the line for transmitting two different signalling impulses, polarized relays provided for repeating the signalling impulses to a local circuit located in each of said stations, polarized relays at each end of the line arranged in cooperation with certain other of the aforementioned polarized relays in such a manner that two different signallin impulses will have an equal and opposite effect regardless of the series resistance of the line and/or the insulation resistance of the line, these impulses being repeated into certain of said polarized relays which form a part of the local circuits, and polarized control relays located in each of said stations whereby the last men-v tioned polarized relays are held to their closed or marking positions during the time that signalling impulses are being transmitted into the line through polarized relays of said local circuits operated through said sending contacts.

2. A telegraph communication system comprising a line, first and second stations connected to each end of said line, sending contacts located in each of said stations, polarized sending relays at each end of the line for transmitting two different signallin impulses, polarized receiving relays for repeating the signalling impulses to a local circuit located in each of said stations. polarized line relays at each end of the line arranged as a part of the polarized receiving relays in such a manner that two different signalling impulses will have an equal and opposite eifect regardless of the series resistance of the line and/or the insulation resistance of the line, these impulses being repeated into said polarized receiving relays, and polarized control relays located in each of said stations whereby said polarized receiving relays are held to their closed or marking positions during the time that signalling impulses are being transmitted into the line by the said polarized sending relays of the local circuits operated from said sending contacts.

3. A telegraph communication system comprising a line, a first and second station connected to each end of said line, a polarized line relay at each end of the line in said stations, each of said stations consisting of a circuit forming sending and receiving means, sending contacts located in each of the sending means of said stations, polarized sending relays in the sending means of each station and controlled by said sending contacts transmitting impulses of positive and negative polarity such impulses operating the line relay at the receiving end of the line in such a manner that the reversal of polarity received by the line relay at the receiving station being transmitted back over the line towards the station transmitting the impulses in such a manner that the operation of the line relay at the receivin end of the line is aflfected in the same manner for both of the signalling impulses received, regardless of the changes in the series resistance of the 8 line and/or the insulation resistance of the line, therefore the algebraic sum of the two signalling impulses is equal to zero for the above mentioned condition.

4. A telegraph communication system comprising a line, a first and second station connected to each end of said line, each of said stations consisting of a circuit forming-a sending and receiving means, a polarized line relay at each end of the line in said stations, sending contacts located in each of the sending means of said stations, polarized sending relays controlled by said sending contacts transmitting impulses of positive and negative polarity, said impulses operating a line relay at the receiving end of the line in such a manner that the reversals of polarity received by the line relay at the receiving station being transmitted back over the line towards the transmitting station in such a manner that the operation of the line relay at the receiving end of the line is affected in the same manner for both of the signalling impulses regardless of changes in the series resistance of the line and/or the insulation resistance of the line, therefore the algebraic sum of the two signalling impulses is equal to zero for the above mentioned line conditions.

5. In a telegraph communication system, a line, a polarized relay at each end of the line, means at each end of the line for transmitting two different signalling impulses and means at each end of the line for receiving two different signalling impulses with means prcvided for repeating these signalling impulses into a local circuit, the said polarized relay arranged as part of the receiving device in such a manner that two different signalling impulses will have an equal and opposite efiect regardless of the series resistance of the line and/or the insulation resistance of the line and means at each end of the circuit whereby the receiving relay is held to its closed or marking contact during the time that signalling impulses are being transmitted into the line by the lrcal circuit, means provided in the apparatus so that when either one of the two signalling impulses are transmitted to the line an equal and opposite polarity is applied at the receiving end of the line in such a manner that the bias current in the line and receiving relay will be reversed for each reversal of polarity applied by the transmitting relay at the sending end of the line, the reversal of polarity at the receiving end in response to reversal of polarityat the sending end is applied to the line at the receiving end by the marking and spacing contact of the line relay at the receiving end in such a manner that the marking and spacing signalling impulses as transmitted from the sending end of the line will have the same effect on the polarized relay connected in the line both for 'marking and a spacing impulse.

SIDNEY ALFRED BARRETT.

REFERENCES CITED The following references are of record in the file of this patent: Y

UNITED STATES PATENTS Number Name Date I 2,131.870 Cramer Oct. 4, 1938 2,133,380 Deardorff Oct. 18, 1938 2,136,984 Smith Nov. 15, 1938 2,140,673 Greene Dec. 20, 1938 2,353,004 Bascom July 4, 1944 

